As a father of four very well-travelled children, let me weigh in here. A six-month old is a heck of a lot easier to travel with than 18 months+, when they start walking and have generally developed an inability to sit still and want to touch and explore everything. There are a number of things you may wish to consider:

- look into approved car seats that have a high degree of recline (stay in your bulkhead seats)
- reduce to two seats if you are able to come up with some contraption/sling where your baby sleeps close to you or his mother
- reduce to two bulkhead seats and leave the baby in the bassinet